1. Field of the Invention
The present invention relates to a light emitting diode (LED) driving circuit, in particular to the LED driving circuit having a metal oxide semiconductor field effect transistor (MOSFET) to improve an input voltage significantly without being limited by the issue of a light leakage.
2. Description of the Related Art
With reference to FIG. 1 for a schematic block diagram of a conventional LED driving circuit, the conventional LED driving circuit comprises an LED driver 12, a driving circuit module 13 and a power supply 14. The LED driver 12 and the driving circuit module 13 of the conventional LED driving circuit are electrically coupled to an LED module 11. The LED driver 12 and the power supply 14 are electrically coupled to each other. The LED driver 12 is provided for receiving a current from the power supply 14 to generate a voltage. The LED module 11 comprises a plurality of light emitting diodes 111. The LED driver 12 comprises at least an enable pin (EN) 121 for receiving a high frequency pulse width modulation (PWM) signal to drive the driving circuit module 13, and the driving circuit module 13 further drives the LED module 12 to achieve illumination.
In the aforementioned conventional circuit architecture, the switching loss is directly proportional to the boost conversion ratio. In other words, the higher the boost conversion ratio, the greater the switching loss would be. To reduce the switching loss, it is necessary to increase the input voltage in order to lower the boost conversion ratio.
However, with a higher input voltage, while the high frequency pulse width modulation signal transmitted from the enable pin 121 is at a low level the forward bias would be significantly high to produce a current passing through the LED module 11, which will lead to light leakage of the LED 111. In order to avoid the light leakage of the LED 111, the input voltage is limited and cannot be sufficiently increased to reduce the switching loss effectively. The aforementioned issues remain to be solved.